The Third Oregon Climate Assessment Report

One major reason for The Climate CIRCulator is that it allows our team members at CIRC and OCCRI to stay up to date on the latest developments in climate science. We do this not just for our own edification, but also because we periodically compile our publication perusing into larger works called climate assessments. In January, our OCCRI team members released their third such assessment to the Oregon Legislature.

Focusing on Oregon, The Third Oregon Climate Assessment Report (OCAR 3), like other climate assessments, takes the mile-high view by examining and assessing the pertinent climate science and climate impacts that we are already seeing and can expect to see more of as the Northwest undergoes climatic change.

The report’s list of climate impacts for Oregon make up the usual suspects that our readers are already familiar with: snowpack and drought, wildfires, and sea level rise, to name a few.

So what’s new in the report? For one thing, 2015 happened; 2015 was the warmest year on record for both Oregon and Washington. Record low snowpack was recorded in both states, compounding the effects of an already historic, multi-year regional drought. The report also includes climate information from OCCRI and CIRC’s recent efforts to improve regional climate modeling and climate projections as well as our work in climate change attribution, or the linking of a given climate or weather event—such as wildfire activity or changes in precipitation—to anthropogenic climate change.

For our readers, a lot of this is going to be old hat. Of course, not everyone is as well read as you, dear reader.

In fact, while roughly 97 percent of the scientific community agrees that climate change is happening and caused by people, only 67 percent of Oregonians believe climate change is happening and only 51 percent believe that it is caused by human activities, according to a study we cite in OCAR 3. (Obviously, these folks don’t read our newsletter. Sad.)

Needless to say, those of us in science communication hoping to fill the glass of collective climate awareness not only passed the half-full mark but to the brimming point have really got our work cut out for us. With that in mind, we invite you to spread the word.

What follows is a smattering of facts and figures from OCAR 3 that you can use to top off your skeptical neighbor’s drink, or just share on social media. We’ve taken pains to keep everything brief but intelligible. To share OCAR 3, copy this link:


Human emissions of greenhouse gases dominated Pacific Northwest warming trend from 1901–2012.

Oregon is projected to warm on average 3­–7°F by the middle decades of this century.

Oregon is projected to warm on average 5–11°F by the late decades of this century.

However, if we start to lower emissions, warming could top off around 2–5°F by the 2050s and 2–7°F by the 2080s.

The Pacific Northwest has already warmed and it’s been clearly shown that natural causes can’t explain the warming.

Oregon, Washington, Idaho, and western Montana have warmed by about 1.1–1.5°F between 1901 and 2012.

Under climate change, Oregon summers are projected to warm more than other seasons.

Extreme heat events in Oregon are expected to increase in frequency, duration, and intensity under climate change.

The year 2015 was the warmest year on record for Oregon.

Winter temperatures in 2015 were 5–6°F above average; record low snowpack resulted.

The Snowpack & Drought:

The 2015 drought resulted from a lack of snowpack due to record high temperatures.

Decreasing snowpack under climate change is impacting and will continue to impact Oregon’s water resources.

During the 2015 drought, winter temperatures in Oregon were 5–6°F above average.

2015 temperatures looked similar to conditions expected to be “normal” by the middle of this century.

2015 was dubbed a “snow drought” because precipitation was normal while high temperatures led to low snow.

In 2015, 25 of Oregon’s 36 counties received official drought declarations.

Mountain snow acts as a natural reservoir for many communities in the Northwest. No snow = no reservoir.

Dependable mountain snowpack is essential for water supply in many Oregon watersheds.

Precipitation in Oregon and the Northwest will fall more as rain and less as snow as the climate warms.

Over the period 1955–2015, mountain snow water equivalent declined at nearly every recording site in Oregon.

Average declines in snow water equivalent in Oregon were about 37% for the years 1955–2015.

For every 1.8°F of warming, snow water equivalent in the Cascades is expected to decline by 22–33%.

Oregon is projected to warm on average 3–7°F by the middle decades of this century.

Oregon is projected to warm on average 5–11°F by the late decades of this century.

Oregon snow water equivalent is expected to decrease by 30% by 2050s under current climate change trajectory.

Oregon snow water equivalent is expected to decrease by 40–50% by 2080s under current climate change trajectory.

Low elevations in the Oregon Cascades are expected to be particularly vulnerable to shifts from snow to rain.

Much of the Cascades and Blue Mountains are expected to transition from snow to rain under climate change.

As snow becomes scarce under climate change, Oregon will need to rely more on stored water to meet summer demand.

The 2015 snow drought resulted in millions of dollars of losses for Washington State farmers.

Human-made climate change exacerbated the 2015 drought in Oregon and Washington.
The 2015 snow drought was influenced by “the Blob,” a mass of abnormally warm seawater off the West Coast.

More snow droughts are expected in the Northwest under climate change.


A loss of snowpack is expected to continue to change the timing and flow of Oregon and Pacific Northwest streams.

Under climate change, higher stream flows are expected during the winter months for many Northwest streams.

Under climate change, many Northwest streams are projected to see lower flows during the summer months.

Northwest stream flow timing has already shifted.

Northwest stream flow timing is now nearly 8 days earlier than the mid-20th century average.

Stream temperatures lethal to fish are expected to increase as snowpack declines and streams lower and warm.

Under climate change, low stream flow extremes in the Northwest are expected to be lower than current lows.

Northwest fish habitat is expected to degrade as stream flows lower under climate change.

Adult salmon migrations could be delayed by lower summer stream flows under climate change.

Young salmons’ migrations to the ocean could be thrown off due to climate change’s affect on stream flows.

Headwaters of Northwest streams are likely to act as cold-water refuges for salmon and other fish.


Climate change led to an additional 16,000 square miles (a doubling) of area burned in wildfires in US West for years 1984–2015.

Wildfires have increased in size and intensity in Western US forest in recent decades.

Climate change led to a doubling of area burned in wildfires in the US West during the years 1984–2015.

The Pacific Northwest endured its worst fire season on record in 2015.

The 2015 fire season cost the Northwest an estimated $560 million in fire suppression costs.

The length of the fire season has grown in recent decades and is expected to continue growing under climate change.

Declining snowpack and earlier spring snowmelt are the primary culprits of the increased fire season length.

Climate change is creating ideal conditions for larger, more destructive wildfires in much of US West.

Under climate change, wildfire activity is expected to increase in Oregon’s Willamette Valley.

Human Health:

Climate change threatens the health of Oregonians.

Heat-related illness and death are expected to increase in Oregon with rising temperatures.

By mid-century, the number of heat-related premature deaths in Portland, Oregon, is expected to increase.

The elderly are expected to be especially vulnerable to heat-related illnesses and death under climate change.

More frequent heat waves under climate change are expected to exacerbate chronic health conditions

Mental health is known to be affected by extreme weather and climate events.

Adaptation efforts, such as adding more air conditioners, may help reduce heat waves’ adverse effects.

Outdoor air quality is expected to worsen under climate change due to increased ground level ozone.

The climate change–induced increase in wildfires is expected to worsen outdoor air quality in the future.

Disease vectors, including ticks and mosquitoes, are expected to increase in Oregon under climate change.

Coastal Hazards:

Under climate change, more flooding and erosion are expected for Oregon Coast as sea levels rise.

On the Oregon coast, sea level could rise by as much as 12–47 inches by the end of this century.

Rising sea levels are expected to put thousands of Oregonians at risk.

The Pacific Northwest coast can experience elevated sea levels during El Niño events.

Coastal erosion amplified on the Pacific Northwest coast during strong El Niño and La Niña events from 1979–2016.

El Niños, big waves, and rising seas are expected to lead to increased erosion and flooding on Oregon’s coast.

Wave heights and strength have increased off the Northwest coast, leading to increased erosion and beach loss.

Ocean Acidification:

In order to lessen climate change’s short-term negative impacts, we need to find ways to adapt.

The world’s oceans have absorbed about a third of the CO2 resulting from human activity.

CO2 in oceans lowers the water’s pH, leading to ocean acidification, a danger to shell-forming creatures.

By lowering available carbonate ions, ocean acidification impairs oysters’ and crabs’ ability to build shells.

West Coast fisheries have already experienced the effects of ocean acidification.

Northwest Tribes:

Climate change threatens the health, sovereignty, and economies of Northwest American Indian tribes.

Climate change is expected to lower the availability and timing of traditional foods, including salmon and shellfish.

American Indian tribes are expected to be some of the first to experience climate change impacts.


Cutting Emissions Won’t Be Enough—Adapt, Adapt, Adapt:

In order to avoid climate change’s long-term negative impacts, we need to reduce our emissions of greenhouse gases.

Efforts to reduce greenhouse gases will not be enough to stop climate change in the short run.

A two-part strategy of greenhouse gas mitigation and climate adaptation is needed.

Oregon’s greenhouse gas emissions peaked in 1999, declining by about 12% from 2005 to 2012.

Oregon needs to lower its emissions even more than it already has to meet its climate goals.

Oregon’s emissions by 2020 are projected to be higher than the target set by the state legislature.

Study: The Third Oregon Climate Assessment Report

Citation: Dalton, M.M, K.D. Dello, L. Hawkins, P.W. Mote, and D.E. Rupp. “The Third Oregon Climate Assessment Report, Oregon Climate Change Research Institute,” College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR. (2017)

Photo Caption: Cover of The Third Oregon Climate Assessment Report. (Photo Credit for Cover Photo: Emily Wisler, all rights reserved.)

Nathan Gilles is the managing editor of The Climate Circulator, and oversees CIRC’s social media accounts and website. When he’s not writing for CIRC, Nathan works as a freelance science writer. Other Posts by this Author. 

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